Preparation of novel B4C nanostructure/Si photodetectors by laser ablation in liquid

Abstract

In this study, boron carbide (B4C) nanoparticles (NPs) are synthesized by pulsed laser ablation of boron in ethanol at a laser fuence of 6.36 J ­cm−2 ­pulse−1. The efect of numbers of laser pulses on the structural, optical, and electrical properties of B4C NPs was studied. X-ray difraction (XRD) results revealed that all B4C nanoparticles synthesized were polycrystalline in nature with a rhombohedral structure. When the laser pulses increased from 500 to 1500, the optical band gap of B4C decreased from 2.45 to 2.38 eV. Fluorescence measurements showed the emission of two emission peaks. The Raman spectra of B4C nanoparticles exhibit six vibration modes centered at 270, 480, 533, 722, 820, and 1080 ­cm−1. Field emission scanning electron microscope (FESEM) images show the formation of spherical nanoparticles of an average size of 68, 75, and 84 nm for samples prepared at 500, 1000, and 1500 pulses, respectively. The dark I–V characteristics of B4C/Si heterojunction photodetectors showed rectifcation characteristics, and the heterojunction prepared at 500 pulses exhibits the best junction characteristics. The illuminated I–V characteristics of B4C/p-Si heterojunction photodetectors exhibited high photosensitivity to white light. The spectral responsivity of the p-B4C/p-Si photodetector shows that the maximum responsivity was 0.66 A ­W−1 at 500 nm for a photodetector prepared at 500 pulses. The highest specifc detectivity and quantum efciency were 2.18× ­1012 Jones and 1.64 × ­102 % at 550 nm, respectively, for a heterojunction photodetector fabricated at 500 pulses, The ON/OFF ratio, rise time, and fall time are measured as a function of the number of laser pulses. The photodetector fabricated at 1500 laser pulses showed roughly rise and fall intervals of 1.5 and 0.8 s, respectively